Since the development of the locomotive, people have attempted to develop systems for warning others about a locomotive or train's pending arrival at a particular point. Whistles, flashing lights, and barricades have all been used as strategies to try to prevent humans from being injured from a moving train. Current systems typically employ a combination of these techniques at various points near and around railroad tracks, junctions, and stations.
Perhaps the most prevalent alarm system is a whistle located on the conductor's engine of the train. A train whistle is extremely loud for the purpose of transmitting a signal for very long distances to give humans (such as those in automobiles and other vehicles) advanced warning before the arrival of a train at an intersection. For example, a train signal may be loud enough such that a human in a car with the windows rolled up may still hear the whistle with enough warning such that the train is at a distance of at least half a mile or a mile away. As a consequence of the decibal level of the train signal necessary to warn humans in automobiles and other vehicles, the train signal can often be heard at a great distance in all directions from the train tracks.
Many train tracks exist in areas where houses and other residential developments exist. As a result, humans living in those areas must suffer through extremely loud train signals throughout the day and even late into the night. This loud noise creates a nuisance, causing property values near the train tracks to be lower than those further away from the train tracks and also causing general displeasure with the train system.
These and other drawbacks exist with current systems.